High-Temperature Electric Properties and X-ray Photoemission Spectra of Layered Co-Based Oxides Bi_(2-x)La_xSr_2Co_2O_(8-δ)  

作　　者：李中华 陈刚 裴健 刘璞生 

机构地区：[1]Department of Applied Chemistry, Harbin Institute of Technology

出　　处：《Journal of Rare Earths》2007年第S1期301-304,共4页稀土学报（英文版）

基　　金：the National Nature Science Foundation of China (20571019);the Project-sponsored by SRF for ROCS ,HLJ (LC06C13);Project-Sponsored by Program of Harbin Subject Chief Scientist (2006RFXXG001);Development Programfor Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2006.028)

摘　　要：Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.Layered Co-based ceramics with a nominal composition Bi2-xLaxSr2Co2O8-δ (x=0.0, 0.4, 0.8, short by BLC-222) were prepared using conventional solid state reaction method. X-ray photoemission spectroscopy (XPS) was used to investigate their electronic structures. The cobalt ions are highly mixed valences of Co3+ and Co4+. The fraction of Co4+ almost keeps unchanged with the increase of x. The O-1s photoemission spectra show that there are lattice oxygen and chemical absorbed oxygen in all the samples. The substitution of Bi3+ by La3+ results in a change from metallic-like behavior to semiconductor behavior. This abnormal phenomenon means that La3+ plays a key role in effecting the electrical transport property of BLC-222. The O-Co covalence bond is strengthened by the increase of La3+, which results in the decrease of conductivity.

关 键 词：layered Co-based ceramic thermalelectric XPS BC-222 rare earths 

分 类 号：O482.4[理学—固体物理]